The cube just exceeded E+7 neutrons

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Finn Hammer
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Real name: Finn Hammer
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Re: The cube just exceeded E+7 neutrons

Post by Finn Hammer »

Rex,

You are right about the configuration. I only use these caps because I bought 1000 of them back some years, for a teslacoil tank capacitor, which didn't make it into actual hardware.
Back in 1999, I entered Tesla coiling, and right at that time, Terry Fritz, Moderator of the Pupman list, had published the first Multi Mini Capacitor capacitor, or MMC.
Facing the task of constructing a homemade oil submerged capacitor from polyetylene foil and allu wrap, (which would have measured 1x2x3 feet) I instead jumped on the MMC wagon, encouraged by Terry. Terry was a good guy, I asked about this and that, and he just answered: "I wouldn't worry too much, Finn, just solder it up and have a go".

And that is why tesla coils from then on had tank capacitors made up from several individual high voltage capacitors.

This following picture from 1999 gives you an idea about what it took to make a cap for a 8 feet discharge tesla coil.

One of the first MMC's from 1999
One of the first MMC's from 1999
First light may 03 1999
First light may 03 1999

In the tesla coil community, we did extensive destructive testing of these caps, and got to know them very well. The 1600V types generally stood up to 3400VDC, at which point the foil punctures, but due to the metallized intermediate electrode, it self heals. I won't go into the current aspect of these caps here, because it is irrelevant at the milliamps we are talking about. These caps can handle tens of RF amps with ease.

The tesla coiling community was extremely collaborative in those days, not many kept secrets, everybody shared their work openly. "You are what you share" seemed to be the mantra, and that is how the tesla coil was brought from esoteric black art into a straightforward engineering practice in less than a decade.

One test I did was to set up a tesla coil that needed 68nF of tank cap. I then made 4 caps: a 1x, a 2x2, a 3x3 and a 4x4
the 1x lasted 10 secs, then fried
the 2x2 lasted 2 minutes
the 3x3 lasted 15 minutes
I never managed to break the 4x4 so for future work, on stuff that went into museum service, I used 5x5 and never heard a word of complaint. The latest coils I have built use the Hocky Puck style high current GTO snubber caps, and I had 50 of them custom made in china. splendid stuff, and if I had to start from scratch today, I would buy fresh caps from china today.

--anyway I degress, but only to give a bit of background on the choice of capacitors, in out of spec. applications.

So, 12 years ago, I bought 10 cases of MMKP383 from Phillips, now Vishay/Beyschlag and you can still get them from Digikey, they have 87 ready to go:
https://www.digikey.com/en/products/det ... hQAMVQXXpA


@2.82$ if you move now.

Best to have a good estimate of the input voltage, you don't want to hook this up to a free running, hopalong style ZVS mazilli driver. Hope this helps.

Cheers, Finn hammer
Matt_Gibson
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Joined: Thu Sep 23, 2021 10:36 am
Real name: Matt Gibson

Re: The cube just exceeded E+7 neutrons

Post by Matt_Gibson »

Finn is correct on the zvs driver…Tried using one last night and it was really erratic and hard to control. It seemed to want to "floor it” constantly.
Rex Allers
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Location: San Jose CA

Re: The cube just exceeded E+7 neutrons

Post by Rex Allers »

Thanks, Finn, for all the info.
On the digikey link it was ~$200 to duplicate your multiplier worth of caps.

I went for it and cleaned out most of their available stock with my order.

I appreciate your sharing from long-term experience, as most here are doing.
Rex Allers
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